The sediment transport on a shoreline depends on the incident wave waves (height and direction). The shoreline diffusivity is a parameter of use in one-line models of shoreline behavior. (See the Java applets for beach fill behavior and the single groin evolution.)

Here you need to input the breaking wave height and wave angle to determine Q, the longshore sediment transport. There is also an empirical constant K that needs to be supplied. Experiments have shown that K is about 0.7. To also determine G, the shoreline diffusivity, you need to input some geometry of the beach profile--the berm height and the depth of closure (the depth beyond which the profile does not change with time).

Assumed values: sand porosity = 0.3, specific gravity of sand= 2.65, breaking index = 0.78. To change the output values of Q and G for a different value of porosity (p), multiply the output values by (1-0.3)/(1-p). For a different specific gravity (s), multiply the output by (2.65 - 1)/(s-1).

The formula used to calculate Q is:

Q = K E_b *C_b*sin(t)*cos(t)/(rho*g*(s-1)*(1-p)
where
K is an empirical coefficient, taken as 0.77
E_b wave energy at breaking
C_b group velocity at breaking
t wave angle at breaking
rho density of water
g acceleration of gravity
s specific gravity of sand
p porosity of sand

Comments: Robert A. DalrympleCenter for Applied Coastal Research
University of Delaware, Newark DE 19716USA